I just got back from a sudden trip to the vet for a fecal exam.
As you might know, around October 13th, I gave all 4 cats a new food, and a few days later, 3 of them started having digestive issues. Yoyo, who is the most easy-going, probably ate the most of this food. Oddly, 2 of them became rather constipated, but Yoyo started having diarrhea.
A number of days after I took them off this food, by October 20th, the 2 that were constipated became normal. Yoyo's bowel movements started getting some form to them, and I thought all was going good.
Yoyo had a really good, normal bowel movement about a week ago.
But then things started getting soft again. Tonight I came home from work, and Yoyo who always loves to poop as soon as he has an audience

went to do his business but oddly, he didn't cover. I went to check and found that he had very muddy diarrhea (no form at all), and that there was a little bit of blood in it.
Needless to say, I took him to the vet right away (actually, I came here to check some info and
then I went to the vet - thank goodness for Itchmo!).
I'd like your opinion on what you think would be good to do.
Yoyo's fecal slide came back with "spots of abnormal bacteria" and there were some white and red blood cells in the sample. For now the vet is assuming it is due to the new food that didn't agree.
Yoyo's weight has not changed, his temperature is normal, his tummy felt normal, his appetite, sleeping, playing, drinking, urinating, everything is completely normal.
Because Yoyo's diarrhea has been on and off now for 3 weeks, he recommended :
1) 5 days, 2x a day of
Metro Nidazol antibiotics + 5 days, 2x a day of probiotics
He said he usually advises 3 days, but he thought 5 days would be better for Yoyo's case. He said he'd start tonight, because the longer I wait might mean that his digestive issues would worsen, and then it would take even longer than 5 days of meds.
(Side affects of Metro Nidazol : vomiting, incontinence

)
I told him I wasn't keen on giving antibiotics unless it was completely and utterly necessary. We talked for some time and he said that if I didn't feel comfortable giving him the antibiotics, that I could do one of these:
A) 24-hour fasting
B) 24-hour fasting + probiotics
C) Regular eating + probiotics
I told the vet I'd research and then decide tomorrow, or even see how Yoyo is tomorrow before deciding what to do...
** As I was writing this, Yoyo suddenly started hissing and growling at the other 3 cats - I've never seen him do that before - I'm going to hope that it has something to do with his being at the vet by himself

-- oh, he's licking himself and I'm wondering if it's from having the sample taken?? After we got home, we all played and had dinner, he had some diarrhea again but all else was normal for an hour...now he is sitting in his favorite spot growling very quietly but calming down **
Any thoughts on this? I dread giving medicine. It's also a little hard to do a fast since there are 3 others (he could stay at my Mom's place, but he's never been there without his sister and I'm afraid that might scare him).
Should I just do as the vet recommends and give him 5 days of the antibiotics + probiotics? Urgh, I hate this.
ETA : It just occurred to me that last night I trimmed off some mats away from Yoyo's bum (probably due to diarrhea) and gave everybody some Weruva fish wet as a treat. Could fish have disrupted Yoyo's digestion?
ETA 2 : Reading on forums about Metronidazol...mine are in small capsules and the vet suggested hiding them in the food or popping them into the back of his throat. The probiotics are also in capsules, and can be hidden in the food or opened and mixed with food (he says cats generally like the flavor of it).